It is frequently necessary to sample or remove a sample from a suspect tissue for testing. In humans, such a sample removal is particularly useful in the diagnosis and treatment of cancerous or pre-cancerous conditions. In the case of suspected cancer, particularly cancer of the breast, early detection and diagnosis is critical to the success of the patient's treatment and recovery.
Various techniques are available to aid in detection and diagnosis, including physical examination and imaging, such as mammography, x-ray, ultrasound, magnetic resonance imaging (MRI), and the like. When a condition is detected that suggests the possibility of cancer, a biopsy can be performed to obtain tissue samples for a complete diagnosis.
One biopsy technique frequently performed is a core biopsy, which uses a core biopsy device in which a cannula is inserted into the tissue of interest, thereby coring a biopsy sample from the tissue having a cross section similar to that of the cannula, and which is retained within the cannula. The cannula, with the biopsy sample, is then removed from the tissue, followed by cytological and/or histological analysis of the sample.
One group of core biopsy devices is based on the combination of a notched inner stylet and an outer severing cannula. The stylet is retained within the lumen of the outer cannula such that the pointed end of the stylet closes off the open end of the cannula. The stylet and cannula are advanced into the tissue mass until they are near the desired biopsy site. The stylet is then advanced relative to the outer cannula to expose the notch to the biopsy site where the tissue prolapses into the notch. The outer cannula is then advanced to sever the tissue in the notch. The disadvantage of this method is that it produces a small core biopsy relative to the outer cannula size since the cross section of the sample is substantially equal to the cross section of the stylet notch, which is substantially smaller than the cross section of the outer cannula. The advantage of this method is that the sample is completely severed from the tissue mass and securely retained within the notch.
Another group of core biopsy devices is based on a coring cannula in combination with a non-notched stylet. The stylet is used to plug the end of the coring cannula during the insertion of the coring cannula into the tissue adjacent the biopsy site. The coring cannula is then advanced relative to the stylet into the biopsy site to retain a sample within the coring cannula. The advantage of this device is that a full core biopsy sample is obtained. That is, the cross section of the sample is substantially equal to the cross section of the coring cannula. The full core sample provides a much larger sample which is highly advantageous.
Some biopsy devices permit the user to select the size or length of the biopsy sample obtained. One such group only allows the user to choose between predetermined sizes or discrete intervals of sizes. Other biopsy devices allow infinite adjustment within a range of possible sizes.